The Chinese patent application No. 200410059061.1 discloses a portable electrocardiograph, whose specification proposes that a neutral electrode can be disposed to eliminate a measurement error which is caused by electrical potential fluctuation of the measured person's body.
However, if the skin of a measured person has an excessively large impedance or has an instable contact with the electrode such that cardiac rate cannot be correctly measured through the electrocardiogram waveform, the pulse rate needs to be measured through a pair of photoelectric cells; or the pulse rate parameter and the blood oxygen saturation parameter are measured independently, further judging whether the pulse rate and the respiratory function of a patient are normal. Unfortunately, it is hard for the measured person to use the portable electrocardiograph and the blood oxygen saturation measuring instrument with his/her two hands simultaneously.
Therefore, the Chinese patent application No. 200410059061.1 cannot simultaneously measure the electrocardiogram and the blood oxygen saturation.
In addition, the neutral electrode provided in the Chinese patent application No. 200410059061.1 is vertical with the longitudinal direction. The shape of the neutral electrode is an elongated rectangular.
Those skilled in the art can easily understand that the case that any finger of any measured person cannot contact the elongated rectangular due to different length of a certain finger of various measured persons and different postures of using the portable electrocardiograph may exist, the so-called neutral electrode may do not work at all.
Conversely, if the neutral electrode is made into a large enough rectangular, the material is wasted and the cost of product is increased, and the shape of the portable electrocardiograph is not beautiful.